Radio receiving method and system



Jan. 21, 1941. H. R. BUTLER 2,229,044.

RADIO RECEIVING METHOD AND SYQTEM Filed Oct. 11, 1939 10 2,1 1 70 Hp}: 11 7.2. 2.1 70 p LPF '24 20 Q P4 r L 5 F i.-

/ g Rgg agomouAL 5L 7 GROUPS A3 L INJECTOR A 1 R. F. I BPF w AMPLIFIER J a ,L

1'5 74 \HPFI/ L8 2.7 W LPF J INVENTOR Hgnr- R. Bullet- ATTORNEY Patented Jan. 21, 1941 UNITED STATES Examiner PATENT OFFICE Henry E. Butler, Verona, N. J assignor to Wired Radio, Inc., New York, N. Y., a corporation of Delaware Application October 11, 1939, Serial No. 298,898

8 Claims.

This invention relates to receiving systems wherein radio signals collected by one or more antennas are distributed to one or more groups of radio receivers, and more particularly to such systems wherein an additional program carrier is injected among the radio signals for distribution therewith.

An object of this invention is to improve and enhance long-wave reception in such systems without changing the normal method of shortwave reception therein.

A further object is to inject a long-wave carrier among collected long-wave radio signals for distribution therewith to a plurality of groups of radio receivers, while permitting said groups to receive short-wave signals on separate antennas.

A specific object is to provide a program injector for serving all radio receivers in a system having several antennas each of which serves a separate group of receivers.

Other objects and advantages of the invention will be apparent from the following description of one illustrative embodiment thereof, with reference to the accompanying drawing which is a diagram of a multi-antenna, single-injector receiving system.

In hotels, apartment houses, and other places where there are many radio receivers, it is customary to connect a convenient number of receivers, or all of them, to one antenna. In many cases several antennas are desirable, each antenna being connected to a separate group of receivers. When an installation includes more than one building, each building may have one or several antennas, with each antenna serving its own group of receivers.

While the present invention is applicable to any such arrangement, the example shown in the drawing has nine antennas, I and la to Ih, inclusive. Each antenna has a downlead 2 connected through a radio frequency transformer 3 to a transmission line 4, one side of which may be grounded as at 5. A plurality of radio receivers 6 served by antenna I are coupled to its transmission line, preferably by means of devices which prevent the receivers from interfering with each other. Such a device may be, for instance, a shielded and grounded radio frequency transformer I, or an attenuation pad 8 which may comprise a series resistance or con-denser, or both resistance and condenser in series in the ungrounded receiver connection. While only a few receivers are shown in the drawing, it should be understood that any convenient number of receivers may be connected to antenna I and that a group 'of receivers (shown only in connection with antenna Ie) may be connected to each of the other antennas Ia to Ih.

According to the present invention, a highpass filter I is inserted in each transmission line 4. These filters are adapted to pass all radio frequency signals which it is desired to transfer directly from each antenna to its group of receivers. Ordinarily this would be only short-wave signals. At a point between transformer 3 and filter II! of antenna I only, a band-pass filter II is connected to transmission line 4 of said antenna. This filter is adapted to pass only those signals which it is desired to treat separately in order to improve the reception thereof, and ordinarily would include the broadcast range of frequencies. From fil'ter I I the selected frequency band is passed through an input transformer I2 to a radio frequency amplifier I3 for amplifying all signals in said band. Transformer I2 preferably has a shield I4 connected to one end of its primary winding and grounded as shown at I5. The output of amplifier I3 is connected through an impedance matching transformer I'I to a distribution system I8 which has branches extending to the vicinity of the transmission lines 4 of the other ei'gh/t antennas. Distribution system I8 preferably is balanced to ground and suitable means are provided for coupling the several transmission lines thereto, including in each case a low-pass filter 20 adapted to pass all frequencies passed by filter II, but to exclude all frequencies passed by filters III. For providing such coupling means in an economical and efficient manner the antennas Ia to Ih may be coupled in pairs by connecting the input sides of two low-pass filters 20 to separate secondaries 2| of a radio frequency transformer, the primary 22 of which is connected to a branch of distribution system I8. The output side of each filter 20 is connected to its transmission line 4 between filter II) and ground 5. The coupling transformers may have separate shields 23 connected to the respective secondaries 2I and grounded as at 24. An additional branch 26 of the distribution system is coupled through a radio frequency transformer 21 and low-pass filter 20 to the transmission line 4 of antenna I at a point on the receiving side of its high-pass filter I0. Transformer 2'! has a secondary 28 and a shield 29 connected thereto and grounded at 30.

In the arrangement above described, the output of amplifier I3 is distributed through the low-pass filters 20 to the respective transmission lines 4 so that the band of frequencies selected 10 collect short-wave signals and to transfer thesame directly to its particular group of receivers through its high-pass filter Hi.

In addition to the above described diversion and amplification of selected long-wave signals,

15 the reception thereof may be further improved by equalizing the levels of said signals as received from various broadcast stations, for instance, as shown in applicant's copending appli- 43 cation Serial N 53 filed January 28, 1939. 20 1th the band selection and distribution means above described, there is also provided an injector 32 for supplying an additional program which is not received over any of the antennas, but which is distributed to all of the receivers con- 25 comitantly with the selected band of signals. The injector may receive a program over wires 33, such as a telephone line or a power circuit; or such program may be picked up by a local microphone or reproducer. Injector 32 comprises some 30 form of modulator-oscillator-amplifier, whereby such program is modulated upon a carrier, the frequency of which is within, or slightly below, the range passed by the band-pass filter I I. The frequency selected for the carrier of injector 32 35 should, however, be spaced at least 10 kilocycles from any of the received signal carriers. For instance, inasmuch as the broadcast band covers the range from 550 to 1600 kilocycles with the carriers spaced at 10 kilocycle intervals, the in- 40 jector carrier frequency may be somewhere between 550 and 400 kilocycles, or it may be some broadcast frequency on which signals are too weak to be receivable. The output 34 of injector 32 at such selected carrier frequency is impressed through an attenuation pad 35 upon the distribution system l8 so that the injected program is thereby made available to every receiver in the system. Such injection may be made either ahead of, or following, the amplifier I3 as may 50 be desirable.

Connections may also be made from the injector output 34 to other antenna groups as indicated in the drawing at 38 and 39. Such other antenna groups may be the same as shown in the drawing, or may comprise different numbers or arrangements of antennas. In this manner a single program source and a single injector make an additional program available to every receiver in the system regardless of the number of antennas employed, or of the number of groups of such antennas. Moreover, the injection of such program and the improvement of reception for the broadcast range of frequencies provided by the above arrangement still permits direct reception of short-wave signals by each antenna and its connected group of receivers.

It should be noted, in connection with the master antenna I, that filter ll, transformer I2,

70 amplifier I3, transformer l1, conductors 28, transformer 21, and filter 20, are in a circuit which by-passes long-wave signals around the filter l0, and that the injector 32 is connected to said bypass circuit. Hence the provision of such a cir- 75 cult and apparatus is sufiicient to apply the invention to a system having only one antenna for all receivers.

While a preferred embodiment of the invention has been shown and described, it is to be understood that the invention is susceptible of 5 use in many radio receiving systems and with various modifications within the scope of the appended claims.

What is claimed as new and original to be secured by Letters Patent of the United States is:

1. In a radio receiving system of the type having a plurality of antennas each individually connected to a separate group of radio receivers, the method for improving reception which comprises, blocking reception of long-wave signals on all but one of said antennas without interfering with the reception of short-wave signals on any of them, selecting and amplifying a band of long waves collected by said one antenna, and distributing the amplified waves to all said groups of radio receivers.

2. The method defined by claim 1, with the added steps of modulating a program upon a long-wave carrier the frequency of which is not being used by the received radio waves, and distributing said modulated carrier to all the groups of radio receivers in the same manner as said amplified long waves are distributed.

3. In a radio receiving system having several antennas respectively connected to separate groups of radio receivers, the method for improving reception which comprises, passing shortwave signals directly from each antenna to its group of receivers, diverting long-wave signals from one only of said antennas, amplifying the diverted signals and distributing them to all said groups of receivers in common, and preventing the direct passage of long-wave signals from all said antennas to said receivers.

4. The method defined by claim 3, with the 40 added step of injecting a locally-modulated longwave carrier among said diverted long-wave signals, but at a difierent frequency than any of the latter, whereby said modulated carrier is distributed to all said receivers concomitantly with said long-wave signals.

5. A radio receiving system having a multiplicity of antennas each connected to its individual group of radio receivers, said antennas being divided into groups, each group comprising 5 a master antenna and a plurality of associated antennas, means for blocking the direct passage of long-wave signals from each antenna to its connected receivers without interfering with the direct passage of short-wave signals thereto, means for diverting a selected band of long-wave signals from each master antenna, means for amplifying the diverted bands separately for each master antenna and for distributing the amplified signals to the receivers of the respective antenna groups; means for receiving a program by wire, means for modulating said program upon a longwave carrier the frequency of which is different from any of the long-wave signals, and injecting said modulated carrier among the amplified signals diverted from each master antenna so that said program is distributed to every receiver in the system.

6. A program injection system comprising, a master antenna and a plurality of other antennas, a transmission line from each antenna to a separate group of radio receivers, a high-pass filter in each transmission line adapted to block radio broadcast signals but to pass short-wave signals,

a band-pass filter connected between said mas- 7 ter antenna and its high-pass filter for diverting signals in the broadcast band, means for amplifying the diverted signals, means including lowpass filters for distributing the amplified signals to each of said transmission lines at points beyond the respective high-pass filters; means for receiving a program over wires and for modulating the same on a broadcast frequency, and means for injecting the program-modulated frequency among said diverted signals whereby the injected program is distributed concomitantly with the latter and is receivable by any of the said radio receivers.

7. A radio receiving system comprising, a plurality of antennas each connected with a separate group of radio receivers, means in each antenna connection for blocking long-wave signals without interfering with the passage of short-wave signals directly from each antenna to its group Examiner of receivers, means for diverting a band of longwave signals from one only of said antennas, and means for amplifying the diverted signals and distributing the same to all said groups of receivers.

8. A radio receiving system comprising, an antenna, a group of radio receivers, means including a high-pass filter for conducting short-wave signals directly from said antenna to said receivers, means for by-passing long-wave signals around said high-pass filter, the latter means comprising a band-pass filter, an amplifier, and a low-pass filter, in that order, means for modulating a program on a long-wave carrier and means connected between said band-pass filter and said low-pass filter for adding said programmodulated carrier to the long-wave signals.

HENRY R. BUTLER. 

